If the body covers one third distance at sped `v_1` , next one third at speed `v_2` and last one third at speed `v_3` , then average speed will be

Options

A. `(v_1 v_2 + v_2 v_3 + v_3 v_1)/(v_1 + v_2 + v_3)`
B. `(v_1 + v_2 + v_3)/3`
C. `(v_1 v_2 v_3)/(v_1 v_2 + v_2 v_3 + v_3 v_1)`
D. `(3v_1 v_2 v_3)/(v_1 v_2 + v_2 v_3 + v_3 v_1)`